Optical navigation devices conventionally use a laser-generated light that reflects off a surface to a detector. The detector includes, for example, a complementary metal-oxide semiconductor (CMOS) imager array. The reflection of the light produces a pattern of speckle that is captured by the CMOS imager. As the device is moved relative to the surface (or vice versa), successive images are rapidly captured and compared to determine the amount of movement. The rate at which images are captured can be used to determine the velocity of movement.
Optical navigation devices generally perform well for tracking two-dimensional movements. For example, an optical mouse very precisely tracks movement along the surface of a mouse pad. However, optical navigation can be problematic in certain applications that involve three-dimensional movements.
Consider, for example, an optical pen that is being used to translate and display a user's handwritten input. As the user “writes” with the optical pen, the characters formed by the user are displayed. The user may need to move backward into what has already been written and displayed, to dot an “i” for example. However, movement of the optical pen back to the location of the “i” is tracked and displayed. In other words, when the optical pen is lifted and moved, the movement of the optical pen continues to be tracked and a trace of the movement is incorporated into the display. As such, movements of the optical pen not intended to be seen are nevertheless visible.
Accordingly, an optical navigation device that performs well in three dimensions would be valuable.